351W F150 4x4 Header-Back?
 

I purchased a set of Flowmaster Headers for my 84' 4x4 F150, and I want to true dual it all the way back. All the Header-back kits online are for the 302 or for the 351w with manifolds, but I can't find any for Header-back for the 351w. Does anyone know someone who sells these or know dimensions so I can get them made?